It is known to secure a nut to a bolt by providing through-holes in the nut and bolt and inserting a locking pin, such as a cotter pin, that passes through the nut and through the bolt. It is also known to pass such a locking pin only through the bolt, but not through the nut. Both ways are practical, but have their disadvantages.
Where the locking pin passes through the nut and through the bolt it is necessary to produce the through-bore after the nut has been tightened. In most instances this production of the through-going bore is cumbersome, since the completed nut and bolt connection may not easily be accessible. Further, keeping the hole in the nut in alignment with the hole through the bolt is a problem and attempts at realignment may actually loosen the nut.
In the instance where the locking pin passes only through the bolt and not through the nut, it is assured that the nut cannot fall off the bolt. However, loosening of the nut is not necessarily prevented. Such loosening of the nut is undesirable. U.S. Pat. No. 5,207,543 (Kirma), issued on May 4, 1993, describes a nut lock in which a helical spring is so configured that a portion of the spring holds the nut while an end leg passes through a cross-bore in the bolt. The arrangement is such that a nut tightening torque moment is exerted on the nut when the locking spring is in place. The just described device is effective for its purpose, but leaves room for improvement, especially with regard to the variability of the relative position of the locking member to the nut.